Railway track circuit apparatus



H. G. WITMER 2,00%,047

RAILWAY TRACK CIRCUIT APPARATUS Filed Aug. 26, 1935 r A I) -1 da/h v15 w F 25 z 16 25 5 m r IF M R. v TI ?ZJZ- Y 1w 1' D dji 22 19 W @8 INVENTOR J4 Har0ld U. M'Zmaz' my BY @RW I HIS ATTORNEY Patented May 14, 1935 UNITED STATES PATENT {FF ICE 2,001,047 I j RMLWAY TRACK oinoorr ArrAa'A'riJs Harold G. Witmer, Pittsburgh, Pa", assignor to The Union Switch & Signal Company, Swisse vale, Pa.,'a corporation of Pennsylvania- Applic'ation August 26, 1933," Serial No.686 ,952

11 Claims. (o1. 246 -349 My invention relates to railway track circuit apparatus, and particularly to apparatus in whichperiodic current is supplied to the traffic rails; and is inthe nature of an improvement on the invention covered by an application of Bernard EsOl-lagan, Serial No. 748,675, filed Octoher 17, l-QS-i. A feature of my present invention is the provision of noveland improved apparatus for-expediting the release of a track relay when a vehicle enters the section'of track with which the relay is associated. Apparatus embodying my invention also provides improved shunting sensitivity of the track circuit. Other features and advantages of my invention will appear as the specification progresses.

I will describe four forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawingFig. 1 is a diagrammatic view showing track circuit apparatus embodying my invention. Fig. 2 is a diagramznaticview similar to Fig. 1 but showing a different form of apparatus at the relay end of the track circuit, and Fig. 3 form of apparatusof Fig. 2, both of which forms also "embody'my invention. Fig. 4 is a diagrammatic view of another form of apparatus embodying my invention, which form obtains the rectified current for saturating the core of the reactor the transformer end of the track circuit.

Similar reference characters refer to similar partsin each of the views.

Referring to Fig. 1, the reference characters land i designate the traffic rails of a railway track which are arranged by insulated rail joints to form a track section A-B. The track section A-B is provided with a track circuit, the essentialelements of which comprise thetraffic rails bonded in the customary manner, a source of current connected across the traffic rails at one end of the section and a track relayenergized by energy taken fromthe traffic rails at the opposi e end of the section. a

Considering the source of current for the track circuit of the section A-B, the secondary winding 3 of a track transformer T has one terminal connected with the rail l over a resistor l and a conductor 5; and its other terminal connected wi h the rail l through the windings 6 and l in series ofa reactor R tobe referred to later and a conductor 8. The primary winding 53 of the transformer T is connected with any convenient source of periodic current such as an alternating current generator not shown in the drawing. It follows that the transformer T constitutes a source of periodic current from whichcurrent is constantly supplied to the traffic rails of the section A-B.

The reactor R may take difierent forms and.

is a view of a modified.

preferably comprises three magnetizable cores It, I! and I2 such, for example, as iron. That is tosay, thereactor R is preferably of the type commonly known to the art as a three-legged" reactor. The windings 6 and I, which are inter posed between the secondary 3 of transformer T and the tramc rail l, are mounted on the two outercores i2 and it; respectively. These windings 5' and i are identical and additive as to mag netomotive force and; consequently, substantially 10 no flux created thereby will pass through the cen ter core H. Mounted on the center core II is a Winding I-3 to which there is supplied unidirec tional current in a manner to appear hereinafter.

When unidirectional current flows in the winding it, the direct current flux from the center core I I' returns through the outside cores it and I2, and the'whole core structure is magnetized. As saturation is approached, the effective permeability of the iron is reduced and the react'an'ce of the 20' windings 6 and l is reduced accordingly. It fol= lowsthat the reactance of the'windings 6 and T of reactor R can, therefore, be controlled by governing the direct current suppliedto the winding !3.

At the relay end of the section A-B, the primary winding M of a transformer Ti has its opposite terminals connected with the traffic rails l and i over conductors i5 and i6, respectively,

a resistor l'i being interposed in the connection 30 with rail l The secondary winding is of the transformer TI is connected across the input terminals of a full-wave rectifier Hi, the output terminals of which are connected'with the winding of a direct current relay TR, and also across the 35 trafiic rails l and F. To be explicit, the output terminal 26 of rectifier I9 is connected with one terminal of the winding of the relay TR by a conductor 28, and is connected with the traflic rail l by the conductors 22 and H5. The output 40 terminal 2| of the rectifier i9 is connected with the opposite terminal of the winding of the relay TR by a conductor 29; and with the rail I over conductor 23', reactor 2t, and conductors 25 and it. It is clear that the periodic current supplied 5 to the traffic rails at the lefthand end of the section A-B is passed by the transformer TI to the rectifier l9, and the track relay TR is energized by a portion of the rectified current, and

the remaining portion of the rectified current is supplied to the traiilc rails.

Referring again to reactor R, the winding 13 has one terminal connectedwith the rail I over conductors 26 and 8, and its other terminal connected with the rail I over conductors 2'! and 5.

The winding it is so proportioned that it offers a relatively high reactance to the periodic current but a relatively low resistance to direct current. Consequently, thedirect current supplied to the traffic rails at the righthand end of the section AB flows in the winding I3 and a direct flux is created thereby. It is to be noted that the windings 8 and i of reactor R, secondary winding 3 of transformer T and the resistor 4 when taken in series, form a parallel path to the winding I3. The parts are so proportioned, however, that the direct current flowing in this last traced path is relatively small and can be neglected.

It is well known in the art that the ballast resistance of track circuits is constantly changing and may vary over wide limits. This wide variation of the ballast resistance makes it difficult to so adjust a track circuit that proper working value of current is obtained when the ballast is Wet, and then not over-energize the track relay when the ballast is dry or frozen. It is also well known that thetrain shunt resistance, that is, the resistance from one trafiic rail to the other through the paths comprising the wheels and. axles of the train, varies greatly for different train weights and speeds, and between bright and rusty conditions of the traffic rails. Essential characteristics of a railway track circuit are reliable energizing of the track relay, shunting sensitivity and the shunting period. The shunting sensitivity of a trackcircuit is the facility with which the track relay is shunted in response to a resistance connected across the traffic rails. That is, if it requires a relatively low resistance path (train shunt) across the traffic rails before the track relay is released the circuit possesses a low shunting sensitivity, and if the track relay is released in response to a relatively high resistance path (train shunt) across the trafiic rails the circuit possesses a high shunting sensitivity. The interval lapsing between the time the leading pair of wheels and axle of a train enter the track section and shunt the traffic rails, and the time the track relay releases constitutes the shunting period of the track circuit.

, Satisfactory operation of the wayside signal depends upon reliable energization of the track relay when the associated track. section is unoccupied, Quick release of the track relay in response I to a vehicle entering the section, and upon the relay remaining down during the entire period the vehicle occupies any part of the section. It is clear, therefore track circuit apparatus that is capable of normally supplying sufiicient energy, that possesses a high shunting sensitivityand that assures a quick release of the relay is essential. Especially is this true when high speed light weight motor cars are to be operated over the track circuit.

I will now describe the operation of the apparatus of Fig. l paying particular attention to the manner wherein the apparatus embodying my invention provides improved performance with respect to the characteristics referred to above. The parts are preferably so proportioned that normally the voltage across the terminals of the secondary winding 3 of transformer T will be approximately twice the voltage across the rails I and i adjacent the lefthand end of the section A--P-. resulting electromotive force applied to the primary winding i i of the transformer Tl will be passed to its secondary winding 18, and hence to the input of the rectifier ii]. That portion or" the rectified output of rectifier Iii supplied to the winding of the track relay TR will have a magnitude equal to the usual working value of current for track relays of the type here involved. That portion of the rectified output of rectifier i9 supplied to the trafiic rails and thence tothe winding [3 ofreactor R. will create a direct current flux sufiicient to substantially saturate the cores of the reactor, and hence the reactance of windings 6 and I will normally have a minimum value.

When a train enters the section A-B, the train shunt greatly reduces the voltage applied across the primary winding 14 of the transformer TI and the magnitude of the current supplied to the winding of the track relay TR will be reduced in the usual manner. The direct current fed back to the traffic rails will also be greatly reduced and, consequently, the magnetic flux created by the winding I 3 of the reactor R will no longer saturate the cores and the reactance of the windings 6 and 1 will be materially increased with the result that the voltage applied across the trail-lo rails will be greatly reduced. This reduction in the voltage applied to the trailic rails will still further reduce the electromotive force available at the transformer Ti, and hence will act to further reduce the current supplied to the track relay TR, and that relay will be quickly released.

It is clear that with apparatus of the type here disclosed the train shunt resistance which will be eifective to bring about a release of the track relay TR will be materially higher than that which is obtained with the usual type of reactor. Furthermore the interval lapsing between the time a train enters the section and the actual release of the track relay will be materially reduced from that which is obtained with customary contemporary equipment. That is to say, the apparatus of Fig. 1 will be effective to normally supply suificient energy for reliable operation of the track relay under usual variations of ballast resistance, to provide a high shunting sensitivity for the track circuit, and to expedite the release of the track relay in response to a train entering the section.

Referring to 2, the trafiic rails I and I re arranged to form a track section AB the same as in Fig. l, and the source of periodic current and the reactor R associated therewith are preferably similar to the corresponding devices of Fig. 1. At the righthand end of the section AB, the primary winding of a transformer T2 has its opposite terminals connected across the trafl'ic rails i and i the resistor I! being inserted in the connection the same as in Fig. l. former T2 is connected across the input terminals of a rectifier 32, the output terminals of which are connected with the winding of the track relay TR. A second secondary winding 33 of transformer T2 is connected across the input terminals of a rectifier 34, the output terminals of which are connected with the traffic rails. To be explicit, the output terminal of rectifier 34 is connected with rail i by a conductor 35; and the output terminal 37 is connected with the rail E by conductor 38, reactor 39, and a conductor 40. It follows that a portion of the energy received from the traflic rails by the transformer T2 is applied to a first rectifier 32, and the rectified output utilized to energize the track relay TR, and the remaining portion of the energy is applied to the input of a second rectifier 34 and the rectlfied output thereof supplied back to the traflic rails. The parts of the apparatus of Fig. 2 are so proportioned and adjusted that the track relay TR is supplied normally with the usual working value of current, and the direct current supplied to the traffic rails is sufiicient to so energize the winding [3 of reactor R that saturation of the cores of the reactor is obtained.

A first secondary winding 3| of trans- The operation of the apparatus oi Fig. 2 in response to a trainenteri-ng the section A--B- will be essentially the 'same in all respects to: the operation ofthe apparatus of Fig. 1, and it is thought not necessary to repeat it in detail. It is clear that with proper proportioning; of the parts of the apparatus of Fig. 2, the shunting sensitivity of the track circuit will be materially higher and the time required to release thetrack relay TR will be materially reduced from that obtained in. present day practice, and at the same time reliable operation of the track relay will be assured,

Fig. 3 a'modified form of Fig. 2 in whichthe direct current track relay TR is replaced by an alternating current track relay'IRi. The sec ondary winding 3 I. of the transiormer'TZ in place ofbeing connected to the input terminals" of a rectifier as shown in Fig. 2 is connected directly with the: terminalsof the winding of the relay and hence relay TRI is directly supplied with, a portion of the alternating current receivedirom the traflic rails. The secondary winding 33 of transformer T2 is connected with.

-i the input terminals of the rectifier 34, and the rectified) output supplied tothe traffic rails over conductors 36: and 38 the same as in Fig. 2. That is to say, in Fig. 3,Japortion of the alternati-ng current obtained from the trafilcrails is utilized to. energize the track relay, and the-remaining portion; of. the alternating current. is converted into unidirectional current and utilized to energize the winding I3 of the reactor R. It is clear that the operation of the apparatus shown in Fig. 3 will besimilar tothat already described for The secondary winding 3 of the track transformer T has one terminal connected with the rail l. over conductor 5; and its opposite terminalconnected with the rail I over windings 6 and. l of reactor R and the conductor 8, the resistor. of Fig. 1 being omitted. The primary winding 40: of a transformer T3 is. connected across the conductors 5 and 8 by the conductors M and 42, respectively. The secondary winding 43 of the transformer T3 is connected with the input terminals of a fu1l-wave rectifier 44, the output terminals of which are connected with the. winding [3 of. reactor R.

The parts, are so proportioned that the rectified. current suppliedthrough the rectifier 44 to the winding [3. is sufficient to create a direct current magnetic flux sufficient to saturate the cores of the reactor R. The train shunt of any train entering the section A-B will cause the voltage supplied" across the primary winding 41! of," the transformer T3 to drop, and hence the current supplied to the winding. l3 will be reduced. It follows that the apparatus of Fig. 4 will'b'e eifective to provide ahigh shunting sensitivity for the track circuit and will also provide a quick release for the track relay TR.

Track circuit apparatus such as here disclosed will have a high shunting sensitivity, a relatiyeiy quick release of the track relay, and at the same time reliable energization of the track will be assured.

only four forms of apparatus embodyingmy invention, it is understood that various changes and modifications may be made therein within the scope of the; appended claims without departingfrom the spirit and scope of my invention'. 1

Having thus described my invention, what I claim L. Incombination with a section of railway track, a source of periodic current, means for connecting said source across the traffic rails of the section including a first winding of areactor having a magnetizable core, a traffic governing relay, means adapted to receive periodic current from the traffic rails for energizing said re lay, other means adapted to receive periodic current from the traflic rails of the section including an asymmetric unit for converting the periodic current into unidirectional current; and

means connected with the output of said asymmetric unit, including the rails ofsaid section and a secondwinding of said reactor, for governing the flux in the core of the reactor.

2. In combination with a section of railway relay, means adapted. to receive periodic current I from the traffic rails for energizing. said relay, other means adapted to receive periodic current from the traffic rails of the section including an asymmetric unit for converting the periodic current into unidirectional current; and a circuit including the output of said asymmetric unit, a rail of said section and a second winding of thereactor; for varying the permeability of the core of said reactor to control the periodic current supplied to the traffic rails.

3. In combination with a section of railway track, a source of periodic current, means for connecting said source across the traffic rails of the section including a first winding of a, reactor having a magnetizable core and a pair of con ductors, a traffic governing relay, means adapted to receive periodic current from the traffic rails for energizing said relay, other means adapted to receive periodic current directly from said pair of'conductors independently of the traffic rails of the section and including an asymmetric unit for converting the periodic current into unidirectional current, and means connected with the output of said asymmetric unit including a second winding of the reactor for governing the flux in the core of. the reactor whereby the 'reacta'nce of said first winding is controlled in accordance with the presence or absence of a train in said section.

4. In combination with a section of railway track, a source of periodic current, means. for connecting said source across the traffic rails. of the section including a first winding of a reactor having a magnetizable core, a second winding mounted on the core of said reactor, circuit means including a source of direct current sup-plied over the rails of said section for energizing said second winding to create a steady magnetic flux for determining the reactance of said first winding, means governed by traffic conditions of said section for controlling said circuit means whereby the voltage of the periodic current supplied across the traffic rails is varied in accordance with the presence or absence of a train in' said section, and receiving means connected across Although I have herein shown and described the trafiic rails of the section including an electroresponsive device effectively influenced by the periodic current.

5. In combination with a section of railway track, a source of periodic current, a reactor having a center and two outside magnetizable cores, means for connecting said source across the trafiic rails of the section including a first and a second winding mounted on the outside cores respectively and arranged in such a manner that magnetomotive forces created thereby are additive, a third winding mounted on the center core, circuit means including a source of direct current supplied over the rails of said section for energizing said third winding to create a steady magnetic flux for determining the reactance of said first and second windings, traffic controlled means responsive to a train entering said section for controlling said circuit means whereby the voltage of the periodic current supplied to the trailic trails is varied in accordance with the presence or absence of a train in said section, and receiving means connected across the traffic rails of the section including an electroresponsive device effectively influenced by the periodic current.

6. In combination with a section of railway track, a source of periodic current, a reactor at one location of the section having a center and two outside iron cores, means for connecting said source across the trafiic rails including a first and a second winding mounted on the outside cores respectively and arranged in such a manner that magnetomotive forces created thereby are additive, a third winding mounted on the center core of the reactor, a first means at the reactor location of the section receiving periodic current from said source and including the input terminals of a full-wave rectifier also at the reactor location, means including the output terminals of said rectifier for supplying unidirectional current to said third winding for controlling the permeability of the cores of said reactor to govern the periodic current supplied to said traific rails, and a second means receiving periodic current from the traffic rails including a traffic governing electroresponsive device.

'7 In combination with a section of a railway track, a source of periodic current, a reactor having a center and two outside magnetizable cores, means for connecting said source across the traffic rails at one end of the section including a first and a second winding mounted on the outside cores respectively and arranged in such a manner that magnetomctive forces created thereby are additive, a third winding mounted on said center core, circuit means including a source of direct current supplied over the traflic rails of the section for energizing said third winding to create a steady magnetic flux for determining the reactance of said first and second windings and thereby control the periodic current, receiving means connected across the traffic rails at the other end of the section to receive the periodic current, a traffic governing electroresponsive device controlled by said receiving means, and trafiic controlled means responsive to a train entering said section for controlling said circuit means.

8. In combination with a section of railway track, a source of periodic current, a reactor having an auxiliary and two main magnetizable cores, means for connecting said source across the traflic rails at one point including a first and 8.

second winding mounted on the two main cores respectively, a first means receiving the periodic current from the traffic rails at another point including the input terminals of a rectifier, means including the output terminals of said rectifier for supplying the rectified current to the trafiic rails, means connected across the trafi'ic rails at said one point including a winding mounted on said auxiliary core and adapted to receive said rectified current to create a magnetic flux in the cores of the reactor for determining the reactance of said first and second windings and thereby control the periodic current, and a second means receiving current from the traffic rails at said other point including an electroresponsive device effectively governed by the periodic current.

9. In combination with a pair of conductors, a source of alternating current, means for connecting said source across said conductors at one point including a-first winding of a reactor having a magnetizable core, receiving means connected across the conductors at another point effectively influenced by said alternating current, operating means controlled by said receiving means, other means controlled by said receiving means including an asymmetric unit and connected across the conductors at said other point for supplying unidirectional current to said conductors, and means connected across the conductors at said one point including a second winding of said reactor'effectively influenced by the unidirectional current for varyingthe permeability of the core of said reactor to control the alternating current supplied to the conductors.

In combination with a section of railway track, a source of periodic current, means for connecting said source across the traffic rails at one end of the section including a first winding of a reactor having a magnetizable core, receiving means connected across the traflic rails at the other end of the section adapted to receive said periodic current, means-governed by said receiving means including an asymmetric unit and connected across the traffic rails at said other end of the section for supplying a portion of the periodic current back to the traflic rails as unidirectional current, and means connected across the traffic rails at said one end of the section including a second winding of said reactor and adapted to receive the unidirectional current for varying the permeability of the core of said reactor to control the periodic current supplied to the traffic rails.

11. In combination with a section of'railway track, a source of periodic current, a reactor'having an auxiliary and two main magnetizable cores, means for connecting said source across the traffic rails at one point including a first and a second winding mounted on the two main cores respectively, a third Winding mounted on the aimiliary core, a transformer having its primary winding connected across the trafiic rails at said one point and its secondary winding connected with the input terminals of a rectifier,'means for connecting the output terminals of the rectifier with said third winding to create a magnetic flux in the cores of the reactor for determining the reactance of said first and second windings, and means connected across the traflic rails at another point of the section including an electroresponsive means effectively controlled by the periodic current.

HAROLD G. WITMER. 

